Personal communications devices with advanced data capabilities and data cards allow mobile computers to connect to the internet wirelessly. These devices create an increasing demand for higher data rate and bandwidth to wireless service providers and operators. To meet these needs, wireless communication systems may use multiple carriers for the transmission of data. A wireless communication system that uses multiple carriers for the transmission of data may be referred to as a multi-carrier system. The use of multiple carriers is expanding in both cellular and non-cellular wireless systems.
A multi-carrier system may increase the bandwidth available in a wireless communication system according to a multiple of how many carriers are made available. For instance, a dual-carrier system may double the bandwidth when compared to a single carrier system and a tri-carrier system may triple the bandwidth when compared to a single carrier system. In addition to this throughput gain, diversity and joint scheduling gains may also be expected. This may result in improving the quality of service (QoS) for end users. Further, the use of multiple carriers may be used in combination with multiple-input multiple-output (MIMO).
As a response to this increased demand in bandwidth, wireless technology continues to evolve. For example, as part of the 3rd Generation Partnership Project (3GPP) specifications, simultaneous use of two High-Speed Downlink Packet Access (HSDPA) downlink carriers has been introduced. In this setup, a base station (which may also be referred to as a Node-B, an access point, site controller, etc. in other variations or types of communications networks) communicates to a wireless transmit/receive unit (WTRU) over two downlink carriers simultaneously. This not only may double the bandwidth and the peak data rate available to WTRUs, but also may increase the network efficiency by means of fast scheduling and fast channel feedback over two carriers. This dual-carrier HSDPA (DC-HSDPA) so far only offers a limited set of HSDPA functionality as it does not support MIMO.
As the data usage continues to increase rapidly, communication systems may use more than two downlink carriers. Multi-carrier operations are proposed to allow multi-carrier aggregation. Multi-carrier operations may allow the WTRU and network to receive/transmit on two or more carriers.
While for dual-carrier the Hybrid automatic repeat request (HARQ) acknowledgment codebook has been specified, a codebook and associated feedback mechanism for more than two carriers is desired.